Illumination of a room is typically provided by a lighting system comprising a plurality of lighting devices. Lighting systems often comprise controllers for controlling the lighting devices in order to provide a desired illumination in an energy efficient manner. In order to further improve energy efficiency or to adapt the illumination to changing conditions in the room, some lighting systems are equipped with sensors, such as motion or presence detectors. In such lighting systems, information from the sensors may for example be used to determine which lighting devices may be switched off or dimmed, without affecting the illumination of occupied parts of the room, in order to save energy.
However, it may be difficult to provide a desired illumination in a room in a sufficiently energy efficient manner. Existing methods of controlling a lighting system are far from optimal in all situations. Hence, it would be desirable to provide an alternative way of controlling lighting systems to achieve a desired illumination in a more energy efficient manner.